PreferenceFragment.java revision 27da0bf0a38231111cbf6bb7df6c4a0d53b144d8
1/* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package android.preference; 18 19import android.app.Activity; 20import android.app.Fragment; 21import android.content.Intent; 22import android.content.SharedPreferences; 23import android.os.Bundle; 24import android.os.Handler; 25import android.os.Message; 26import android.view.LayoutInflater; 27import android.view.View; 28import android.view.ViewGroup; 29import android.widget.ListView; 30 31/** 32 * Shows a hierarchy of {@link Preference} objects as 33 * lists. These preferences will 34 * automatically save to {@link SharedPreferences} as the user interacts with 35 * them. To retrieve an instance of {@link SharedPreferences} that the 36 * preference hierarchy in this fragment will use, call 37 * {@link PreferenceManager#getDefaultSharedPreferences(android.content.Context)} 38 * with a context in the same package as this fragment. 39 * <p> 40 * Furthermore, the preferences shown will follow the visual style of system 41 * preferences. It is easy to create a hierarchy of preferences (that can be 42 * shown on multiple screens) via XML. For these reasons, it is recommended to 43 * use this fragment (as a superclass) to deal with preferences in applications. 44 * <p> 45 * A {@link PreferenceScreen} object should be at the top of the preference 46 * hierarchy. Furthermore, subsequent {@link PreferenceScreen} in the hierarchy 47 * denote a screen break--that is the preferences contained within subsequent 48 * {@link PreferenceScreen} should be shown on another screen. The preference 49 * framework handles showing these other screens from the preference hierarchy. 50 * <p> 51 * The preference hierarchy can be formed in multiple ways: 52 * <li> From an XML file specifying the hierarchy 53 * <li> From different {@link Activity Activities} that each specify its own 54 * preferences in an XML file via {@link Activity} meta-data 55 * <li> From an object hierarchy rooted with {@link PreferenceScreen} 56 * <p> 57 * To inflate from XML, use the {@link #addPreferencesFromResource(int)}. The 58 * root element should be a {@link PreferenceScreen}. Subsequent elements can point 59 * to actual {@link Preference} subclasses. As mentioned above, subsequent 60 * {@link PreferenceScreen} in the hierarchy will result in the screen break. 61 * <p> 62 * To specify an {@link Intent} to query {@link Activity Activities} that each 63 * have preferences, use {@link #addPreferencesFromIntent}. Each 64 * {@link Activity} can specify meta-data in the manifest (via the key 65 * {@link PreferenceManager#METADATA_KEY_PREFERENCES}) that points to an XML 66 * resource. These XML resources will be inflated into a single preference 67 * hierarchy and shown by this fragment. 68 * <p> 69 * To specify an object hierarchy rooted with {@link PreferenceScreen}, use 70 * {@link #setPreferenceScreen(PreferenceScreen)}. 71 * <p> 72 * As a convenience, this fragment implements a click listener for any 73 * preference in the current hierarchy, see 74 * {@link #onPreferenceTreeClick(PreferenceScreen, Preference)}. 75 * 76 * <a name="SampleCode"></a> 77 * <h3>Sample Code</h3> 78 * 79 * <p>The following sample code shows a simple preference fragment that is 80 * populated from a resource. The resource it loads is:</p> 81 * 82 * {@sample development/samples/ApiDemos/res/xml/preferences.xml preferences} 83 * 84 * <p>The fragment implementation itself simply populates the preferences 85 * when created. Note that the preferences framework takes care of loading 86 * the current values out of the app preferences and writing them when changed:</p> 87 * 88 * {@sample development/samples/ApiDemos/src/com/example/android/apis/preference/FragmentPreferences.java 89 * fragment} 90 * 91 * @see Preference 92 * @see PreferenceScreen 93 */ 94public abstract class PreferenceFragment extends Fragment implements 95 PreferenceManager.OnPreferenceTreeClickListener { 96 97 private static final String PREFERENCES_TAG = "android:preferences"; 98 99 private PreferenceManager mPreferenceManager; 100 private ListView mList; 101 private boolean mHavePrefs; 102 private boolean mInitDone; 103 104 /** 105 * The starting request code given out to preference framework. 106 */ 107 private static final int FIRST_REQUEST_CODE = 100; 108 109 private static final int MSG_BIND_PREFERENCES = 1; 110 private Handler mHandler = new Handler() { 111 @Override 112 public void handleMessage(Message msg) { 113 switch (msg.what) { 114 115 case MSG_BIND_PREFERENCES: 116 bindPreferences(); 117 break; 118 } 119 } 120 }; 121 122 final private Runnable mRequestFocus = new Runnable() { 123 public void run() { 124 mList.focusableViewAvailable(mList); 125 } 126 }; 127 128 /** 129 * Interface that PreferenceFragment's containing activity should 130 * implement to be able to process preference items that wish to 131 * switch to a new fragment. 132 */ 133 public interface OnPreferenceStartFragmentCallback { 134 /** 135 * Called when the user has clicked on a Preference that has 136 * a fragment class name associated with it. The implementation 137 * to should instantiate and switch to an instance of the given 138 * fragment. 139 */ 140 boolean onPreferenceStartFragment(PreferenceFragment caller, Preference pref); 141 } 142 143 @Override 144 public void onCreate(Bundle savedInstanceState) { 145 super.onCreate(savedInstanceState); 146 mPreferenceManager = new PreferenceManager(getActivity(), FIRST_REQUEST_CODE); 147 mPreferenceManager.setFragment(this); 148 mPreferenceManager.setOnPreferenceTreeClickListener(this); 149 } 150 151 @Override 152 public View onCreateView(LayoutInflater inflater, ViewGroup container, 153 Bundle savedInstanceState) { 154 return inflater.inflate(com.android.internal.R.layout.preference_list_fragment, 155 container, false); 156 } 157 158 @Override 159 public void onActivityCreated(Bundle savedInstanceState) { 160 super.onActivityCreated(savedInstanceState); 161 getListView().setScrollBarStyle(View.SCROLLBARS_INSIDE_OVERLAY); 162 163 if (mHavePrefs) { 164 bindPreferences(); 165 } 166 167 mInitDone = true; 168 169 if (savedInstanceState != null) { 170 Bundle container = savedInstanceState.getBundle(PREFERENCES_TAG); 171 if (container != null) { 172 final PreferenceScreen preferenceScreen = getPreferenceScreen(); 173 if (preferenceScreen != null) { 174 preferenceScreen.restoreHierarchyState(container); 175 } 176 } 177 } 178 } 179 180 @Override 181 public void onStop() { 182 super.onStop(); 183 mPreferenceManager.dispatchActivityStop(); 184 } 185 186 @Override 187 public void onDestroyView() { 188 mList = null; 189 mHandler.removeCallbacks(mRequestFocus); 190 super.onDestroyView(); 191 } 192 193 @Override 194 public void onDestroy() { 195 super.onDestroy(); 196 mPreferenceManager.dispatchActivityDestroy(); 197 } 198 199 @Override 200 public void onSaveInstanceState(Bundle outState) { 201 super.onSaveInstanceState(outState); 202 203 final PreferenceScreen preferenceScreen = getPreferenceScreen(); 204 if (preferenceScreen != null) { 205 Bundle container = new Bundle(); 206 preferenceScreen.saveHierarchyState(container); 207 outState.putBundle(PREFERENCES_TAG, container); 208 } 209 } 210 211 @Override 212 public void onActivityResult(int requestCode, int resultCode, Intent data) { 213 super.onActivityResult(requestCode, resultCode, data); 214 215 mPreferenceManager.dispatchActivityResult(requestCode, resultCode, data); 216 } 217 218 /** 219 * Returns the {@link PreferenceManager} used by this fragment. 220 * @return The {@link PreferenceManager}. 221 */ 222 public PreferenceManager getPreferenceManager() { 223 return mPreferenceManager; 224 } 225 226 /** 227 * Sets the root of the preference hierarchy that this fragment is showing. 228 * 229 * @param preferenceScreen The root {@link PreferenceScreen} of the preference hierarchy. 230 */ 231 public void setPreferenceScreen(PreferenceScreen preferenceScreen) { 232 if (mPreferenceManager.setPreferences(preferenceScreen) && preferenceScreen != null) { 233 mHavePrefs = true; 234 if (mInitDone) { 235 postBindPreferences(); 236 } 237 } 238 } 239 240 /** 241 * Gets the root of the preference hierarchy that this fragment is showing. 242 * 243 * @return The {@link PreferenceScreen} that is the root of the preference 244 * hierarchy. 245 */ 246 public PreferenceScreen getPreferenceScreen() { 247 return mPreferenceManager.getPreferenceScreen(); 248 } 249 250 /** 251 * Adds preferences from activities that match the given {@link Intent}. 252 * 253 * @param intent The {@link Intent} to query activities. 254 */ 255 public void addPreferencesFromIntent(Intent intent) { 256 requirePreferenceManager(); 257 258 setPreferenceScreen(mPreferenceManager.inflateFromIntent(intent, getPreferenceScreen())); 259 } 260 261 /** 262 * Inflates the given XML resource and adds the preference hierarchy to the current 263 * preference hierarchy. 264 * 265 * @param preferencesResId The XML resource ID to inflate. 266 */ 267 public void addPreferencesFromResource(int preferencesResId) { 268 requirePreferenceManager(); 269 270 setPreferenceScreen(mPreferenceManager.inflateFromResource(getActivity(), 271 preferencesResId, getPreferenceScreen())); 272 } 273 274 /** 275 * {@inheritDoc} 276 */ 277 public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, 278 Preference preference) { 279 if (preference.getFragment() != null && 280 getActivity() instanceof OnPreferenceStartFragmentCallback) { 281 return ((OnPreferenceStartFragmentCallback)getActivity()).onPreferenceStartFragment( 282 this, preference); 283 } 284 return false; 285 } 286 287 /** 288 * Finds a {@link Preference} based on its key. 289 * 290 * @param key The key of the preference to retrieve. 291 * @return The {@link Preference} with the key, or null. 292 * @see PreferenceGroup#findPreference(CharSequence) 293 */ 294 public Preference findPreference(CharSequence key) { 295 if (mPreferenceManager == null) { 296 return null; 297 } 298 return mPreferenceManager.findPreference(key); 299 } 300 301 private void requirePreferenceManager() { 302 if (mPreferenceManager == null) { 303 throw new RuntimeException("This should be called after super.onCreate."); 304 } 305 } 306 307 private void postBindPreferences() { 308 if (mHandler.hasMessages(MSG_BIND_PREFERENCES)) return; 309 mHandler.obtainMessage(MSG_BIND_PREFERENCES).sendToTarget(); 310 } 311 312 private void bindPreferences() { 313 final PreferenceScreen preferenceScreen = getPreferenceScreen(); 314 if (preferenceScreen != null) { 315 preferenceScreen.bind(getListView()); 316 } 317 } 318 319 /** @hide */ 320 public ListView getListView() { 321 ensureList(); 322 return mList; 323 } 324 325 private void ensureList() { 326 if (mList != null) { 327 return; 328 } 329 View root = getView(); 330 if (root == null) { 331 throw new IllegalStateException("Content view not yet created"); 332 } 333 View rawListView = root.findViewById(android.R.id.list); 334 if (!(rawListView instanceof ListView)) { 335 throw new RuntimeException( 336 "Content has view with id attribute 'android.R.id.list' " 337 + "that is not a ListView class"); 338 } 339 mList = (ListView)rawListView; 340 if (mList == null) { 341 throw new RuntimeException( 342 "Your content must have a ListView whose id attribute is " + 343 "'android.R.id.list'"); 344 } 345 mHandler.post(mRequestFocus); 346 } 347} 348